Screen tension detection method and system

Abstract

This application relates to a method and system for detecting screen printing tension. The method involves acquiring a sequence of images of the entire screen release and rebound process of the screen under test using an image acquisition device. The instantaneous rebound speed of the screen under test is extracted by analyzing the image sequence. Based on the instantaneous rebound speed and a preset three-segment tension-rebound speed standard calibration model, the tension range of the screen under test is determined. According to the tension range of the screen under test, corresponding operation instructions are output, improving the accuracy of tension detection and proactively mitigating the risk of hidden printing defects.

Description

Technical Field

[0001] This application relates to the field of screen printing equipment technology, and in particular to a method and system for detecting screen tension. Background Technology

[0002] Screen printing is a core process in photovoltaic cell manufacturing, and screen tension is a key parameter that directly determines the uniformity of printed grid lines, aspect ratio, screen removal quality, and yield. Traditional screen tension detection relies on handheld tension meters for contact-based point detection, requiring machine shutdown, screen removal, and offline sampling. This method is unsuitable for high-speed continuous printing production and cannot capture the fatigue creep and gradual tension decay of the screen during production in real time. Furthermore, handheld tension meters only obtain tension values ​​and cannot distinguish between a screen in a normal elastic working state and one in a state of plastic damage failure. Hidden screen defects can easily lead to poor batch printing. Therefore, improving the accuracy of screen tension detection is an urgent problem to be solved. Summary of the Invention

[0003] Therefore, it is necessary to provide a screen tension detection method and system that can improve the accuracy of tension detection, in order to address the above problems.

[0004] The first aspect of this application provides a method for detecting screen printing tension, including: Acquire the image sequence of the entire process of screen removal and springback captured by the image acquisition device; Based on the analysis of the image sequence of the entire screen rebound process, the instantaneous rebound velocity of the screen under test is extracted; Based on the instantaneous rebound speed and the preset three-stage tension-rebound speed standard calibration model, the tension range of the screen under test is determined; wherein, the three-stage tension-rebound speed standard calibration model characterizes the tension-rebound speed correspondence in the low tension sluggish range, the elastic linear optimal range, and the plastic saturation failure range. Based on the tension range of the screen under test, output the corresponding operation instruction information.

[0005] In one embodiment, the instantaneous rebound speed of the screen printing plate under test is extracted by analyzing the image sequence of the entire screen-free rebound process. This includes: extracting images from the image sequence of the entire screen-free rebound process at preset time intervals; calculating the screen printing plate rebound speed once based on the extracted images; and averaging the screen printing plate rebound speeds calculated from the image sequence of the entire screen-free rebound process a preset number of times to determine the instantaneous rebound speed of the screen printing plate under test.

[0006] In one embodiment, calculating the screen rebound speed based on the extracted images includes: selecting the image with the greatest screen pressure from the extracted images, analyzing the selected image to determine the maximum screen displacement distance and the corresponding maximum pressure time; selecting the image of the screen returning to its initial position from the extracted images, and determining the corresponding recovery time; determining the screen recovery time based on the maximum pressure time and the recovery time, and calculating the screen rebound speed based on the maximum screen displacement distance and the screen recovery time.

[0007] In one embodiment, based on the tension range of the screen under test, corresponding operation instruction information is output, including: if the tension range of the screen under test is a low tension sluggish range or a plastic saturation failure range, a screen replacement command is output; if the tension range of the screen under test is an elastic linear optimal range, the screen is normal; if the tension of the screen under test is at the upper or lower limit of the elastic linear optimal range, a warning and process compensation command are output.

[0008] In one embodiment, before determining the tension range of the screen printing plate under test based on the instantaneous rebound speed and the preset three-stage tension-rebound speed standard calibration model, the method further includes: tensioning the photovoltaic screen printing standard screen printing plate with different tension levels, continuously acquiring a set number of image sequences of the entire process of screen removal and rebound under each tension level; the set number of times is greater than the preset number of times; analyzing the image sequences of the entire process of screen removal and rebound acquired a set number of times, calculating the average rebound speed under each tension level as the standard rebound speed; and performing graded linear fitting based on the standard rebound speed under different tension levels to determine and save the three-stage tension-rebound speed standard calibration model.

[0009] In one embodiment, the tension and standard rebound speed change linearly in the low tension sluggish interval and the elastic linear optimal interval, and the linear slope of the low tension sluggish interval is less than the linear slope of the elastic linear optimal interval; the tension fluctuation range in the plastic saturation failure interval is within the preset allowable fluctuation range, so that the slope of the fitting curve approaches 0.

[0010] In one embodiment, after performing graded linear fitting based on the standard rebound speed under different tension levels and saving the three-segment tension-rebound speed standard calibration model, the method further includes: repeating the calibration by changing screens with different mesh counts, cross-validating the three-segment tension-rebound speed standard calibration model, and / or, using a contact tension meter to measure the tension point by point for offline comparative verification.

[0011] A second aspect of this application provides a screen printing plate tension detection system, including an image acquisition device and a control device, wherein the control device is connected to the image acquisition device and is used to perform screen printing plate tension detection according to the method described above.

[0012] In one embodiment, the image acquisition device is a high-speed camera with an acquisition frame rate of ≥2000fps and an exposure time of 1~10μs.

[0013] In one embodiment, the system further includes a storage device connected to the control device for storing a three-stage tension-rebound speed standard calibration model.

[0014] The aforementioned screen printing tension detection method and system acquires an image sequence of the entire screen release and rebound process captured by an image acquisition device. Based on the analysis of this image sequence, the instantaneous rebound velocity of the screen is extracted. Using the instantaneous rebound velocity and a preset three-segment tension-rebound velocity standard calibration model, the tension range of the screen is determined. Based on this tension range, corresponding operation instructions are output, improving the accuracy of tension detection and proactively mitigating the risk of hidden printing defects. Attached Figure Description

[0015] Figure 1 This is a flowchart of a screen tension detection method in one embodiment; Figure 2 This is a schematic diagram of instantaneous rebound velocity analysis in one embodiment; Figure 3 This is a structural block diagram of a screen tension detection system in one embodiment. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. It is understood that the term "connection" in the following embodiments, if the connected circuits, modules, units, etc., transmit electrical signals or data to each other, should be understood as "electrical connection," "communication connection," etc.

[0018] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0019] Traditional screen tension detection relies on handheld tension meters for contact-based, point-to-point testing, requiring machine shutdown, screen removal, and offline sampling. This approach is unsuitable for high-speed, continuous printing production and cannot capture the fatigue creep and gradual tension decay of the screen during production in real time. Furthermore, current technologies only obtain tension values ​​and cannot distinguish between a screen in a normal elastic working state and one in a state of plastic damage failure. Hidden screen defects can easily lead to poor batch printing. Additionally, the industry currently only has a positive qualitative understanding that "tension affects rebound effect," and has not yet developed a technical solution for inversely quantifying and determining screen tension and elastic health through rebound dynamics characteristics. There is a lack of standardized, online-implementable tension criterion models. Existing industry-standard technologies have the following inherent defects: 1. The tension detection method is outdated and offline. Traditional screen printing tension detection relies on handheld tension meters for contact measurement, which requires stopping the machine, lifting it away from the printing station, and performing point-to-point detection, making it unsuitable for high-speed continuous printing conditions.

[0020] 2. Inability to capture the tension decay process in real time. During continuous production, screen printing plates experience fatigue creep and gradual tension decay. Traditional methods can only perform periodic spot checks and cannot detect minute tension changes in real time, leading to fluctuations in batch printing quality.

[0021] 3. Inability to distinguish between the elastic range and the plastic failure range. Existing technology can only read the "current tension value" and cannot determine whether the screen is in the effective elastic working range, nor can it identify over-tension plastic damage or hidden screen breakage risks.

[0022] 4. Limitations of traditional understanding. The industry only has a positive qualitative understanding of "tension affects rebound," and there is no technical solution to reverse-quantify and determine the tension state using rebound dynamic parameters, no three-segment interval criterion, and no online detection model.

[0023] Based on this, this application provides a screen printing tension detection method, aiming to solve the technical pain points of existing screen printing processes, such as lagging tension detection, inability to monitor online, inability to identify tension decay and plastic failure, and inability to match high-speed mass production. This method acquires an image sequence of the entire screen release and springback process of the screen under test using an image acquisition device. Based on the analysis of this image sequence, the instantaneous springback velocity of the screen under test is extracted. According to the instantaneous springback velocity and a preset three-segment tension-springback velocity standard calibration model, the tension range of the screen under test is determined. Based on the tension range of the screen under test, corresponding operation instructions are output, achieving non-contact, online, and real-time quantified screen printing tension detection based on the dynamic characteristics of the screen's springback velocity. This improves the accuracy of tension detection and proactively avoids the risk of hidden printing defects.

[0024] In one embodiment, a screen tension detection method is provided, applicable to the TOPCon screen printing process for photovoltaic cells, or other processes requiring screen printing. For example... Figure 1 As shown, the method includes: Step S110: Acquire the image sequence of the entire process of screen removal and springback captured by the image acquisition device. The screen under test can be a photovoltaic screen printing screen or other types of screen. The image acquisition device is connected to a control device to control image acquisition and simultaneously output trigger signals to control the downward and upward (screen removal) actions of the squeegee, thereby acquiring the image sequence of the entire process of screen removal and springback captured by the image acquisition device.

[0025] The type of image acquisition device is not unique. In one embodiment, the image acquisition device is a high-speed camera with an acquisition frame rate ≥2000fps, and 3000fps is recommended for critical detection. The requirement is based on the fact that the entire screen printing plate rebound process takes only 8~30ms; a low frame rate will lose instantaneous rebound displacement data, making it impossible to calculate the instantaneous rebound speed. When the high-speed camera's acquisition frame rate is set to 2000fps, the single frame time interval is 0.5ms, which can meet the requirements for micron-level displacement capture. Furthermore, the image resolution of the high-speed camera can be set to 1280×1024 pixels, with a target surface of 1 / 1.8 inches and a pixel size of 4.8μm. The exposure time of the high-speed camera can be set to 1~10μs to eliminate ambient light trailing in the printing workshop.

[0026] The control device can be, but is not limited to, various personal computers, laptops, smartphones, tablets, and portable wearable devices, such as smartwatches, smart bracelets, and head-mounted devices. The control device incorporates an image recognition algorithm that can perform sub-pixel edge recognition on images acquired by the image acquisition device, with a displacement measurement accuracy of ±0.5μm and a rebound speed calculation accuracy of ±0.1mm / s, ensuring accurate calculation of the screen displacement.

[0027] Step S120: Analyze the image sequence of the entire screen removal and springback process to extract the instantaneous springback velocity of the screen under test. After acquiring the image sequence of the entire screen removal and springback process from the image acquisition device, the control device analyzes each image in the acquisition order to extract the instantaneous springback velocity of the screen under test. The control device can obtain the instantaneous springback velocity of the screen under test by analyzing the image sequence of the entire screen removal and springback process acquired by a single blade pressing and lifting; or it can obtain the average springback velocity by analyzing the image sequence of the entire screen removal and springback process acquired by multiple blade pressing and lifting, and use this average value as the instantaneous springback velocity of the screen under test.

[0028] In one embodiment, step S120 includes: extracting images from the image sequence of the entire screen removal and rebound process at preset time intervals, calculating the screen rebound speed once based on the extracted images; averaging the screen rebound speeds calculated from the image sequence of the entire screen removal and rebound process collected a preset number of times to determine the instantaneous rebound speed of the screen to be tested.

[0029] The specific values ​​for the preset time interval and preset number of times are not unique and can be set according to actual needs. For example, the preset time interval can be 1 to 3 ms. The shorter the preset time interval, the more accurate the data read and analyzed from the image, but the control cost will increase. It can be set according to actual needs. In this embodiment, the preset time interval is 2 ms. The control device extracts the longitudinal displacement of the screen center point at 0 ms (the moment the blade is lifted), 2 ms, 4 ms, 6 ms, and 8 ms from the image sequence of the entire screen removal and rebound process.

[0030] Specifically, the screen rebound speed is calculated based on the extracted images, including: selecting the image with the greatest screen pressure from the extracted images, analyzing the selected image to determine the maximum screen displacement distance and the corresponding maximum pressure time; selecting the image of the screen returning to its initial position from the extracted images, and determining the corresponding recovery time; determining the screen recovery time based on the maximum pressure time and recovery time, and calculating the screen rebound speed based on the maximum screen displacement distance and screen recovery time.

[0031] In this embodiment, the maximum longitudinal displacement distance of the screen center point is taken as the maximum displacement distance of the screen, such as... Figure 2As shown, the horizontal axis represents time t (in seconds), and the middle axis represents the longitudinal displacement x (in mm) of the screen center point. 0~t1 represents the printing time when the squeegee presses down on the screen, and t1~t2 represents the screen recovery time at the moment the squeegee is lifted. The control device extracts multiple images at 2ms intervals, finds the image with the largest pressing distance, and combines the maximum pressing distance in the image with the ratio of the image distance to the actual object distance to determine the maximum longitudinal displacement distance x1 (negative value) of the screen center point, and the corresponding maximum pressing time t1. The control device then combines the extracted images to find the initial position of the screen before being pressed down, determining the recovery time t2. The screen rebound speed can then be calculated as Δx / Δt, where Δx = 0 - x1, and the screen recovery time Δt = t2 - t1.

[0032] Furthermore, the preset number of times can be 3 to 6. The scraper performs one downward and upward movement, the image acquisition device acquires an image sequence of the entire screen rebound process, the control device calculates the screen rebound speed once, and the average of the screen rebound speeds calculated multiple times is used to obtain the instantaneous rebound speed V of the screen under test.

[0033] Step S130: Determine the tension range of the screen under test based on the instantaneous rebound velocity and the preset three-stage tension-rebound velocity standard calibration model. The three-stage tension-rebound velocity standard calibration model characterizes the tension-rebound velocity correspondence in the low-tension sluggish range, the optimal elastic linear range, and the plastic saturation failure range.

[0034] Screen tension is the core elastic power source for screen delamination and repositioning. The elastic stored energy generated by the tensioning of the mesh is directly determined by the screen tension, and the two form an inherent dynamic correlation, which can be divided into three characteristic intervals: The optimal range of elastic linearity: Within the limit range of mesh elastic deformation, the greater the screen tension, the higher the elastic energy storage of the mesh, the faster the instantaneous rebound speed after printing pressure relief, and the better the uniformity of screen removal across the entire area. The rebound speed is in a stable positive correlation with the effective tension.

[0035] Low tension sluggish range: When the screen tension is lower than the process standard threshold, the elastic energy storage is insufficient and the rebound driving force is insufficient, resulting in characteristics such as slow rebound, screen removal lag, and prolonged response time, which correspond to defects such as printing tail, false printing, and uneven line thickness.

[0036] Plastic saturation failure range: When the tension exceeds the elastic limit of the mesh, the mesh undergoes irreversible plastic deformation, the elastic energy storage is completely lost, and if the tension is further increased, the rebound speed will no longer increase and the uniformity of rebound across the entire area will deteriorate, resulting in permanent damage to the mesh and a significant reduction in its service life.

[0037] Based on the aforementioned three-stage correlation characteristics, this application uses the rebound speed dynamic parameters as a quantitative basis to reversely determine the tension state and elastic health state of the screen.

[0038] In one embodiment, before step S130, the method may further include: tensioning a standard photovoltaic screen printing plate with different tension levels, continuously acquiring a set number of image sequences of the entire process of screen removal and rebound under each tension level; analyzing the set number of image sequences of the entire process of screen removal and rebound, calculating the average rebound speed under each tension level as the standard rebound speed; and performing graded linear fitting based on the standard rebound speed under different tension levels to determine and save a three-segment tension-rebound speed standard calibration model.

[0039] The set number of times is greater than the preset number, which can be 40 to 60 times. In this embodiment, the set number of times is 50 times. In the low tension sluggish interval and the elastic linear optimal interval, the tension and the standard rebound speed change linearly, and the linear slope k1 of the low tension sluggish interval is less than the linear slope k2 of the elastic linear optimal interval. In the plastic saturation failure interval, the tension fluctuation range is within the preset allowable fluctuation range (for example, the maximum tension difference is less than the preset fluctuation threshold), so that the slope of the fitting curve approaches 0.

[0040] Specifically, a standard stainless steel screen printing plate for photovoltaics (commonly 620 mesh, 6μm wire diameter, standard photovoltaic pattern) can be selected. A pneumatic screen stretching machine is used for graded tensioning, setting tension gradients of 5N / cm, 6N / cm, 7N / cm, 8N / cm, 9N / cm, 10N / cm, 11N / cm, 12N / cm, 13N / cm, 14N / cm, and 15N / cm. The standardized testing environment at the workstation is set as follows: squeegee speed 300mm / s, squeegee pressure 0.4MPa, squeegee lifting height 1.5mm, and photovoltaic front-side silver paste to eliminate printing variable interference. The screen is allowed to stabilize for 30 minutes after each tension setting to eliminate tension stress before testing. High-speed camera captures springback displacement curves: For each tension setting, 50 consecutive image sequences of the entire springback process of a standard stainless steel mesh are captured. The longitudinal displacement of the mesh center point is extracted at 0ms (the instant the blade is lifted), 2ms, 4ms, 6ms, and 8ms. The springback velocity of the mesh is calculated once, and the average of the 50 calculated springback velocities is taken as the standard springback velocity V under that tension. Finally, linear fitting is performed based on the standard springback velocities under different tension settings, dividing the mesh into three boundary segments as follows: Low tension sluggish range: T≤6N / cm, perform a linear fit on the (T, V) data, the fitting function is V=k1·T+b1.

[0041] The optimal range for elastic linearity is T = 7~11 N / cm. For a first-order linear fit, V = k2·T + b2, where k2 > k1, the slope of the positive correlation is the largest.

[0042] Plastic saturation failure range: T > 11 N / cm, the slope of the fitted curve approaches 0, V ≈ constant, and the tension increase rate does not increase significantly.

[0043] By collecting the rebound speed corresponding to different tension levels, the overall tension-rebound speed curve is fitted. The curve is divided into three segments according to the slope. The first segment with a slope of k1 corresponds to the low tension sluggish interval. The second segment with a slope of k2 (k2 is greater than k1) corresponds to the optimal elastic linear interval. The third segment with a slope close to 0 corresponds to the plastic saturation failure interval. Thus, the upper and lower limit thresholds (including tension threshold and rebound speed threshold) of each interval are determined.

[0044] Specifically, the test conditions were set as follows: 620-mesh stainless steel photovoltaic screen, ambient temperature 25℃, standard front silver paste, high-speed camera frame rate set to 3000fps, and the average of 50 tests was taken. The test results are shown in Table 1.

[0045] Table 1 Based on the analysis of Table 1, the interval division is as follows: 1. Low tension slow range 5~7 N / cm: The rebound speed increases slowly with the increase of tension, and the linear slope k1≈1.8.

[0046] 2. The optimal range for elastic linearity is 7~11 N / cm: the rebound speed is strongly positively correlated with the tension, the linear slope is k2≈2.2, the quantitative correspondence is stable, and the tension can be accurately deduced.

[0047] 3. When the tension exceeds 11 N / cm, the rebound speed increases by less than 0.1 mm / s per 1 N / cm, tending to saturate, and the mesh undergoes irreversible plastic deformation.

[0048] Actual testing showed that the model designed using this method can accurately identify abnormal screen tension with 100% accuracy, effectively preventing defects in batch printing.

[0049] In one embodiment, the method may further include: repeating calibration with different mesh sizes to cross-validate the three-segment tension-rebound speed standard calibration model, and / or conducting offline comparative verification by measuring tension point-by-point using a contact tension meter. For example, repeating calibration with three different mesh sizes (520 / 620 / 720 mesh) verifies that the three-segment interval pattern remains unchanged, with only minor adjustments to the fitting coefficients, thus proving the model's universality. During offline comparative verification, tension is measured point-by-point using a commercial contact steel mesh tension meter and compared with the tension inferred from visual inspection in this application. The error within the elastic range is ≤0.8 N / cm, verifying the model's accuracy.

[0050] Furthermore, the three-stage tension-spring speed standard calibration model can also set corresponding tension-spring speed relationships for different types of screens (such as screens with different mesh counts). Thus, during actual printing tension testing, the corresponding tension-spring speed relationship can be selected from the three-stage tension-spring speed standard calibration model according to the actual mesh count of the screen to be tested, and the tension range of the screen to be tested can be determined, making the analysis more accurate.

[0051] After analyzing and determining the three-segment tension-rebound speed standard calibration model, the piecewise fitting function and the upper and lower limits of the interval (7N / cm, 11N / cm) can be written into a storage device to form an industrial control database for use during actual printing tension testing. The storage device can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. RAM can take various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0052] In actual printing tension testing, after the control device determines the instantaneous rebound speed of the screen to be tested, it can directly and accurately determine the tension range of the screen to be tested by combining the saved three-segment tension-rebound speed standard calibration model.

[0053] Step S140: Output corresponding operation instruction information according to the tension range of the screen to be tested. After determining the tension range of the screen to be tested, the control device can output corresponding information according to the correspondence between the tension range and the operation instruction information so that the operator knows the test results.

[0054] In one embodiment, step S140 includes: if the tension range of the screen under test is a low tension sluggish range or a plastic saturation failure range, then output a screen replacement command; if the tension range of the screen under test is an elastic linear optimal range, then the screen is normal; if the tension of the screen under test is at the upper or lower limit of the elastic linear optimal range, then output a warning and process compensation command.

[0055] Specifically, when the tension range of the screen under test is in the low tension sluggish range or the plastic saturation failure range, it indicates a problem with the screen's elasticity. Continuing production will lead to a batch of defective products, requiring screen replacement. Therefore, a screen replacement command is issued to remind the operator to replace the screen. When the tension range of the screen under test is in the elastic linear optimal range, it means the screen tension is within the range and normal production is possible. When the tension of the screen under test is at the upper or lower limit of the elastic linear optimal range, a warning and process compensation command are issued to remind the operator to check and confirm, and adjust the printing press process parameters to ensure normal production. The printing press process parameter adjustment can be adjusting the upper or lower limit of the elastic linear optimal range, or it can be adjusting other parameters. Taking the adjustment of the upper or lower limit of the elastic linear optimal range as an example, because the screen tension will decrease with screen use, there are two possible scenarios after adjusting the process parameters: 1. After adjusting the lower limit of tension, it can be used normally for a period of time, but it will not return to the elastic linear optimal range and will eventually fall into the low tension sluggish range; 2. Adjusting the upper limit of tension will return it to the elastic linear optimal range, and the screen can be used normally.

[0056] The screen printing tension detection method provided in this application is based on the high-speed visual screen rebound dynamics characteristics for online detection and process compensation of screen printing tension. This method utilizes a high-speed, non-contact visual acquisition system to collect millisecond-level rebound displacement data at the moment of screen removal during printing. It establishes a unique three-stage tension-rebound velocity dynamic correlation model to achieve real-time determination, interval classification, and anomaly warning of screen tension status. The overall working logic is as follows: high-speed camera acquisition is triggered synchronously by the printing squeegee action → instantaneous rebound velocity is extracted → the three-stage model intelligently determines the tension status → outputs screen replacement / warning + process compensation commands. The entire process is non-stop, non-contact, and fully automated, suitable for high-speed continuous printing conditions in photovoltaic production lines.

[0057] In one embodiment, such as Figure 3As shown, a screen printing plate tension detection system is also provided, including an image acquisition device 110 and a control device 120. The control device 120 is connected to the image acquisition device and is used to perform screen printing plate tension detection according to the method described above. The image acquisition device 110 is a high-speed camera with a frame rate ≥2000fps and an exposure time of 1~10μs. The control device 120 can be, but is not limited to, various personal computers, laptops, smartphones, tablets, and portable wearable devices. Portable wearable devices can be smartwatches, smart bracelets, head-mounted devices, etc.

[0058] In one embodiment, the system further includes a storage device 130 connected to the control device 120, the storage device 130 being used to store a three-stage tension-rebound speed standard calibration model. The storage device 130 may include at least one of non-volatile and volatile memory.

[0059] It is understood that the specific embodiments of the above-described screen printing tension detection system have been explained in detail in the above-described screen printing tension detection method, and will not be repeated here. The screen printing tension detection method and system provided in this application have the following advantages: (1) Innovative detection logic: Breaking through the limitations of positive cognition in the industry, it pioneered a detection model for reverse quantification of tension based on rebound parameters, filling a technological gap in the industry and possessing outstanding novelty and creativity.

[0060] (2) Enables online non-destructive testing: No need to stop the machine or contact the screen, adaptable to high-speed mass production scenarios, and can capture minute tension decay changes in real time.

[0061] (3) Accurately distinguish fault types: It can simultaneously identify three types of states: insufficient tension, fatigue decay, and plastic failure, and avoid hidden printing defects in advance.

[0062] (4) Improve mass production stability: Significantly reduce defects such as screen printing trailing and false printing, and improve the consistency of photovoltaic cell grid line printing and batch yield.

[0063] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0064] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for detecting screen tension, characterized in that, include: Acquire the image sequence of the entire process of screen removal and springback captured by the image acquisition device; Based on the analysis of the image sequence of the entire screen rebound process, the instantaneous rebound velocity of the screen under test is extracted; Based on the instantaneous rebound speed and the preset three-stage tension-rebound speed standard calibration model, the tension range of the screen under test is determined; wherein, the three-stage tension-rebound speed standard calibration model characterizes the tension-rebound speed correspondence in the low tension sluggish range, the elastic linear optimal range, and the plastic saturation failure range. Based on the tension range of the screen under test, output the corresponding operation instruction information.

2. The method according to claim 1, characterized in that, Based on the analysis of the image sequence of the entire screen rebound process, the instantaneous rebound velocity of the screen under test is extracted, including: Images are extracted from the image sequence of the entire screen removal and springback process at preset time intervals, and the screen springback speed is calculated based on the extracted images. The average value of the screen rebound velocity obtained by collecting the image sequence of the entire screen rebound process for a preset number of times is used to determine the instantaneous rebound velocity of the screen to be tested.

3. The method according to claim 2, characterized in that, The screen rebound velocity is calculated based on the extracted image, including: The image with the greatest screen pressure is selected from the extracted images. The selected image is analyzed to determine the maximum displacement distance of the screen and the corresponding maximum pressure time. Select the image from the extracted images to restore the screen to its initial position, and determine the corresponding restoration time. The screen recovery time is determined based on the maximum pressure moment and the recovery moment, and the screen rebound speed is calculated based on the maximum screen displacement distance and the screen recovery time.

4. The method according to claim 1, characterized in that, Based on the tension range of the screen under test, output corresponding operation instructions, including: If the tension range of the screen under test is a low tension sluggish range or a plastic saturation failure range, then output a screen replacement command. If the tension range of the screen under test is within the optimal range of elastic linearity, then the screen is normal; If the tension of the screen under test is within the upper or lower limit of the optimal range of elastic linearity, then an early warning and process compensation command will be output.

5. The method according to any one of claims 1 to 4, characterized in that, Before determining the tension range of the screen under test based on the instantaneous rebound speed and the preset three-stage tension-rebound speed standard calibration model, the following steps are also included: The standard screen printing plate for photovoltaic screen printing was stretched using different tension levels. At each tension level, a set number of image sequences of the entire process of screen breakage and rebound were continuously acquired; the set number of times was greater than the preset number of times. Analyze the image sequence of the entire process of the netting rebound collected a set number of times, calculate the average rebound speed under each tension level, and use it as the standard rebound speed; By combining the standard rebound speed under different tension levels, a three-stage tension-rebound speed standard calibration model was determined and saved.

6. The method according to claim 5, characterized in that, In the low-tension sluggish range and the elastic linear optimal range, the tension and the standard rebound speed change linearly, and the linear slope of the low-tension sluggish range is less than that of the elastic linear optimal range; the tension fluctuation range in the plastic saturation failure range is within the preset allowable fluctuation range, so that the slope of the fitting curve approaches 0.

7. The method according to claim 5, characterized in that, After combining the standard rebound speed under different tension levels to perform graded linear fitting, and determining and saving the three-segment tension-rebound speed standard calibration model, the process also includes: repeating the calibration by changing screens with different mesh counts, cross-validating the three-segment tension-rebound speed standard calibration model, and / or, using a contact tension meter to measure the tension point by point for offline comparative verification.

8. A screen printing tension detection system, characterized in that, It includes an image acquisition device and a control device, wherein the control device is connected to the image acquisition device and is used to perform screen tension detection according to any one of claims 1 to 7.

9. The system according to claim 8, characterized in that, The image acquisition device is a high-speed camera, with an acquisition frame rate of ≥2000fps and an exposure time of 1~10μs.

10. The system according to claim 8, characterized in that, It also includes a storage device connected to the control device, the storage device being used to store a three-stage tension-rebound speed standard calibration model.

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